Fuse for the safe and precise detonation of explosive projectiles

ABSTRACT

A detonating fuse for a fired, spinning projectile, which fuse includes a primer-supporting rotor which is prevented from being moved from a safety to a firing position by means of a springbiased safety lever. The safety lever is prevented from swinging out, under the influence of centrifugal force, by means of a rotatable spring core member. The core member is locked against rotation by an anchor until the projectile is fired at which time the anchor is released and the core member is rotated in a predetermined angle by a draw spring to release the safety lever. Continued rotation of the core member releases a pair of swingable levers to enable a biasing means to push a firing pin into the rotor which has been moved to its firing position by centrifugal force. The core member and safety lever further include mutually engageable stops to prevent unintentional detonation during transport.

United States Patent Kaiser et al.

FUSE FOR THE SAFE AND PRECISE DETONATION OF EXPLOSIVE PROJECTILES Filed:

Inventors:

Appl. No.:

Paul Kaiser, Schramberg; Rudolf Weber, Schramberg-Sulgen, both of Germany Firma Gebruder J unghans G.m.b.H., Schramberg, Germany Dec. 9, 1971 Foreign Application Priority Data Dec. 15, 1970 Germany ..P 20 61 765.6

US. Cl.....

Int. Cl......

References Cited UNITED STATES PATENTS Baker ..l02/7l Primary Examiner--Samuel Feinberg Att0rneyJames E. Cockfield [5 7] ABSTRACT A detonating fuse for a fired, spinning projectile, which fuse includes a primer-supporting rotor which is prevented from being moved from a safety to a firing position by means of a spring-biased safety lever. The safety lever is prevented from swinging out, under the influence of centrifugal force, by means of a rotatable spring core member. The core member is locked against rotation by an anchor until the projectile is fired at which time the anchor is released and the core member is rotated in a predetermined angle by a draw spring to release the safety lever. Continued rotation of the core member releases a pair of swingable levers to enable a biasing means to push a firing pin into the rotor which has been moved to its firing position by centrifugal force. The core member and safety lever further include mutually engageable stops to prevent unintentional detonation during transport.

15 Claims, 9 Drawing Figures II 1 38 11 .J H 33b 23 fi IV PATENTEB HAY 2 21975 SHEET 3 [IF 4 FUSE FOR THE SAFE AND PRECISE DETONATION OF EXPLOSIVE PROJECTILES The invention relates to a fuse for the detonation of fired, spinning projectiles, which fuse includes a firing pin and a primer-containing rotor disposed between the point of the firing pin and an explosive charge.

In the present invention, the rotor is in a safety position prior to discharge of the shot, in which position the primer lies outside the range of movement of the firing pin. A safety element is provided which engages a stop recess of the rotor in the safety position. The safety element is provided with a thread and is moved out of the recess by means of a safety nut activated upon the release of a centrifugal strip. A further safety device is provided for restraining the firing pin, and includes a draw spring. The draw spring, after a decrease in the spinning of the projectile, and at a predetermined time, releases the firing pin for movement toward the primer.

BACKGROUND AND OBJECTS OF THE INVENTION Mechanical, self-destroying shell fuses for small caliber projectiles have been known in which the time for, or occurrence of, self-destruction is controlled by the amount of rpm, or spinning of the projectile, i.e., merely by the centrifugal force. In the case of other self-destroying fuses, however, the times for selfdestruction are controlled by a clock mechanism.

The fuse of the former case, in which the time for self-destruction is controlled merely by the centrifugal force, can be produced at a relatively low cost. In such fuses however, the occurrence of self-destruction is not precise but rather fluctuates depending on the amount of spinning, which can be changed by many influencing conditions. For example, the projectiles might leave the muzzle of the barrel with a different or unexpected amount of spinning. Also depending on the angle of elevation during release of the shot and the elevation from sea level at the place where the shot is fired, the atmospheric density will change, which somewhat decellerates the spinning. Moreover, very large variations in the atmospheric pressure also have their effect on self-destruction in the case where projectiles are fired against or from airplanes. The range or spread of the self-destruction times under certain circumstances can lead to endangering ones own troops. Also, such fuses have a very small muzzle safety i.e., an initial safe travel in which detonation cannot occur, which typically is about meters.

Draw spring control fuses have good muzzle safety and transportation safety. Also, with such fuses one can achieve comparatively precise self-destruction times. Such fuses however, are more difficult to produce and therefore more expensive.

A spin-controlled fuse is currently known, as shown in US. Pat. No. 2,790,390, which is provided with a thread-control of the firing pin. There the attempt has been made by means of a very simple threaded mechanism to control the muzzle safety, which safety approaches the characteristics of the type of fuse which is operated by a draw spring. This case concerns a fuse of the initially mentioned type, and wherein a draw spring, attached at one end to a fuse housing, is looped around a rotor. The draw spring is cocked during spinning, counter to its drawing force, and consequently will turn the rotor which is attached to its other end. At

the same time a firing pin, which can be shifted only longitudinally, is shifted, by means of a thread, from its position securing the rotor toward the point of the fuse. When the spinning decreases, the draw force of the draw spring exceeds the centrifugal force and the firing pin is screwed in a reverse direction into the rotor which has been swiveled in the meantime into the primed position, and the primer is pierced. According to a modification, a flexible strip, which is attached at one end to the rotor and at the other end to the fuse housing, is wound around the rotor. This strip pulls a draw spring, which engages against a bore of the fuse housing under spring tension, onto a rotor attachment in a direction counter to its tension force as a result of centrifugal force created by the spin. When the spin declines and the centrifugal force acting on the flexible strip exceeds, after a certain time, the tension force of the cocked draw spring, then the flexible strip again is rolled onto the rotor by means of the draw spring, and the firing pin is moved in the direction of the primer.

While the construction of the above-described patent is very simple, a sufficient muzzle safety cannot be achieved with this simple construction. Also, the occurrence of self-destruction cannot be predicted with sufficient precision, since the firing pin is moved only slowly toward the primer. Thus, the danger exists that a selfdestruction will not occur with any or enough certainty. Moreover, the achieveable degrees of precision are not sufficient.

A very simple fuse construction with a draw spring drive and a thread control mechanism has been disclosed in Austrian Pat. No. 79,395 which, however, 0perates independently of the projectile spin. This known fuse construction results in a sufficient functional safety while spinning occurs, since a control disk employed therein cannot be moved by centrifugal force during spinning. However, the amount of safety that is provided during transportation is entirely insufficient.

The present invention has as its primary objective the provision of a fuse of the initially mentioned type which can be produced at low cost, while having maximum muzzle safety and enabling a precise adjustment of the self-destruction occurrence to be made.

It is an additional object of the invention to provide a fuse which can be produced with very small dimensions, so that it can be used for small caliber projectiles, such as 3.5 cm shells.

SUMMARY OF THE INVENTION The above objects, among others, will be achieved according to the present invention in which a safety nut is mounted freely rotatably and concentrically around a firing pin. The safety nut is connected, by way of a threaded arrangement, to a safety bushing which serves as a safety element. The safety bushing can be shifted longitudinally and encloses the firing pin with clearance.

A device which includes a draw spring has a spring core for driving a timing mechanism and is freely rotatable about the firing pin. The spring core has a first, lower extension on its front surface, i.e., the surface facing the safety nut, in order to release a lock mechanism which secures the safety nut.

The spring core further includes, on its front side facing away from the safety nut, a threaded, upper extension. A movable nut is guided on the upper extension for rotationless, longitudinal shifting. In one of its terminal positions the movable nut secures a lock device for a spring which would otherwise move the firing pin in the direction of the primer.

The lock mechanism which secures the safety nut preferably consists of a pivotally mounted safety lever having a recess. The safety lever can be pivoted from a rest or safety position by centrifugal force. In its safety position the safety lever encloses one end of the safety nut in a positive locking manner. The safety lever preferably includes, in its recess, a lug which reaches behind the lower extension of the spring core to prevent the latter from being rotated by a cocked-spring. The lower extension of the spring core has a recess which, after being turned by a predetermined angle, releases the lug.

Preferably, the recess of the safety lever will include a notch such that, if the lower extension of the spring core should turn while the safety lever is in its safety position, the lower extension of the spring core will jam in this notch to prevent further turning.

The timing mechanism of the fuse preferably consists of a single gear arranged on the spring core, a drive wheel driven by this gear and connected with a speed gear and an anchor driven by the speed gear. The anchor is pivotally mounted on the lower extension of the spring core and serves to regulate the rotation of the spring core.

A lock for the firing pin consists of at least one lever pivotally mounted outside of the firing pin. In its inwardly swung position the lever forms a stop for the firing pin. The lever can be swung outwardly, under the influence of centrifugal force. The lever is provided with an arm extending to the bore of a movable nut, the lever being released only after a predetermined longitudinally shift of the movable nut. The movable nut has a crosssection of noncircular form, preferably a polygonal cross-section. A guide element surrounds the movable nut and prevents it from turning.

The locking lever for the firing pin may be mounted on this guide element. Preferably, the guide element is mounted on a spring housing containing the draw spring and has been provided with projecting tabs which engage recesses in the spring housing.

THE DRAWINGS The invention will be explained in more detail in the following paragraphs on the basis of the drawing and a preferred embodiment given by way of example.

In the drawing:

FIG. 1 shows a longitudinal section through a fuse according to the invention, taken along line II of FIG.

FIG. 2 shows a section taken along line II-II of FIG. I, in which the lever securing the firing pins is in a safety position,

FIG. 3 shows a section taken along line IIIIII of FIG. 1, showing the spring housing and the spring core,

FIG. 4 shows a section taken along line lV-IV of FIG. 1, showing the drive mechanism for the spring core,

FIG. 5 shows a section taken along line VV of FIG. 1 through the braking arrangement for the spring core,

FIG. 6 shows a section taken along line Vl-VI of FIG. 1, which shows the release mechanism for the muzzle safety device,

FIG. 7 is an enlarged view of the lock mechanism for the safety nut,

FIG. 8 shows a section taken along line VIIIVIII of FIG. 1, and

FIG. 9 shows a section taken along line IX-IX of FIG. 1.

In the drawings, with the exception of FIG. 7, the individual elements of the fuse are shown in their safe state. The entire fuse structure is essentially divided into two main assembly portions, or groups, which are in operative connection with one another. One of these portions establishes the muzzle safety while the second portion defines the self-destroying arrangement.

The entire fuse is located inside a fuse housing 10, which is screwed onto a bursting charge or projectile, such as a grenade. The assembly portion which establishes muzzle safety consists of a safety nut 13 with a centrifugal strip 14, which nut may also be designated as the core nut. The safety nut 13 is mounted rotatably in a plate 12 in the fuse body 11, the latter being threadably attached to the fuse housing 10. The safety nut 13 has a polygonal circumference on which has been wound a centrifugal strip 14, known in the art, and which can consist, for example, of aluminum. The centrifugal strip 14 is held together by a steel loop 15.

The safety nut 13 has an inside bore which is slidably penetrated by a firing pin 35. The inside bore of the safety nut 13 has a thread 13a into which a safety element, or bushing, 40, being provided with an outside thread, is screwed.

In the position shown in FIG. I, the safety bushing is in its lower, safety position in which it engages, with its pointed end, a stop portion of the rotor. The stop portion is preferably in the form of a stopping recess 16a in the rotor 16, which rotor contains a primer 17. Consequently, the rotor 16 is held in the position shown in FIG. 1, in which the primer 17 is located outside the range of movement of the firing pin 35. By turning the safety nut 13, it is possible to unscrew the safety bushing from the stopping recess 16a. It will be apparent that the stop portion of the rotor may consist of an outwardly projecting lug which is engageable within the central bore of the safety bushing 40, in lieu of the stopping recess 16a.

The safety nut 13 normally is secured in its safety position of FIG. 1 by means of a safety lever 20, which lever is pivotally mounted on a pivot pin 19. The safety lever 20 has two recesses 20a and 20b, shown also in FIGS. 6 and 7. The recess 20a has two parallel surfaces extending around corresponding outside surfaces of the safety nut 13 in the safety position to prevent the latter from turning. The safety lever, in its solid-line safety position of FIG. 6, is held by means of a leaf spring 21.

The second recess 20b of the safety lever 20 encompasses a first, lower extension 22a of a spring core member 22, the spring core member being connected to a draw spring 24. The lower extension 22a of the spring core 22 has a lateral recess and thus forms two stop surfaces 220 and 22a;; to prevent the spring core 22 from rotating (see FIG. 7). The preipheral surface of the lower extension 22a is designated by a reference character 22a The recess 20!) of the safety lever 20 further includes a lug 200 which engages behind the stop surface 22a of the lower extension 22a of the spring core whenever the lower extension 22a is in the safety position shown in FIG. 6. The safety lever 20 in such case cannot be swung out of the position shown in FIG. 6 by centrifugal force, occurring during discharge of the projectile,

because the lug 200 of the safety lever extends behind the stop surface 22a The second assembly portion, as noted previously, causes the self-destruction of the projectile whenever the latter has not reached its target after a predetermined time. This portion comprises the spring core 22, already described, with the draw spring 24, the latter being disposed in a fixed or stationary spring housing 23. The spring core 22 is rotatably mounted in a plate 29 and in a cover member 30 which covers the spring housing. The spring core 22 is freely penetrated by the firing pin 35 and contains a spring 38 which holds the firing pin in its rest position shown in FIG. 1. The spring core 22, as already explained, has its lower extension 22a projecting into one end of the safety nut 13 and, as previously explained, thus causes the securing of the safety lever 20.

In order to ensure a predetermined operation of the spring core 22, a second timing mechanism has been provided which consists of a gear 25 attached to the spring core, a drive wheel 26 driven by the gear 25, a gear wheel 27 drivingly connected with the drive wheel 26, and an anchor 28 driven by the gear wheel 27, as illustrated in FIGS. 1, 4 and 5. The anchor 28 is rotatably mounted on the spring core 22 and is held, prior to discharge of the projectile, by two metal flaps 39, so that the timing mechanism cannot run down.

The metal flaps 39, during discharge of the projectile are moved outwardly as a result of the centrifugal force caused by the spinning of the projectile as shown in dash-dot lines in FIG. 5. As a result, the anchor 28 is released and the timing mechanism begins to run down.

The gear wheel 27 and the anchor 28 are arranged such that, as the gear wheel 27 rotates, it must cam open the anchor. Thus, the anchor offers resistance to the rotation of the gear wheel and tends to regulate somewhat the turning of the spring core. If desired, a spring may be provided to bias the anchor or escapement 28 to a neutral position (perpendicular to a radius of wheel 27 or vertical in FIG. 5) to increase the resistance which must be overcome by the gear wheel 27.

The spring core 22, on its end facing away from the safety nut 13, is provided with a second, upper extension 22b having an outside thread. A movable nut 31 is screwed onto this outside thread, which nut 31 has an outside periphery that is non-circular, being preferably polygonally shaped. The movable nut 31 is guided in a guide element 33 within a recess formed by a portion 33a of the guide element. This guide element conforms to the outside periphery of the movable nut 31 to prevent the latter from turning, while permitting it to move axially.

The movable nut 31 has an inside bore 31a which, in the position shown in FIG. 1, receives two arms 32a of two safety levers 32 for controlling the firing'pin 35 (see FIG. 2). The safety levers 32 are pivotally mounted on pivot pins 37. The safety levers form stops, Le, a restraining mechanism, for a firing bushing or self-destroying element 34, which is biased by a spring 36. Upon release, the spring 36 causes a movement of the firing pin in the direction of the primer 17.

After a predetermined turning of the spring core 22, the movable nut 31 is moved in a direction toward the cover of the spring housing, to such a point that it will assume a lowered, dash-dot position as shown in FIG. 1. In this position the bore 31a is no longer able to contain the arms 32a of the levers 32. As a result of the centrifugal force caused by the projectile rotation, the levers 32 are moved toward the outside as shown in dash-dot lines in FIG. 2. As a result, the levers 32 are moved away from the striking bushing 34, and the bushing can move the striking pin toward the primer 17.

It should be noted that the safety bushing 40 is guided by means of two parallel surfaces 11a in body 1 l of the fuse, as shown in FIG. 9. These surfaces 11a extend against corresponding surfaces 40a of the safety bushing and prevent the latter from turning, while permitting an axial shifting of the safety bushing.

Prior to discharge of the projectile, the parts are in the position shown in FIG. 1. In this position the fuse is largely protected from all imaginable influences. Even if a shaft of the timing mechanism, for example, the one mounting the drive element 26 and the gear wheel 27, should break in the event of the projectile being dropped, a discharge is not possible. Such is the case since the surface 22a;, of the lower extension 22a of the spring core will strike the lug 200 in the recess 20b of the safety lever 20 after a predetermined turn of the spring core. As a result, the lower extension 22a of the spring core has its stop surface 22a;, and its peripheral surface 22a, jammed into a notch 20d, formed by the lug 200 as shown in FIG. 7, to prevent further rotation. The safety lever 20 will not swing outwardly since it is biased by the spring 21. Thus, in the case of either an impact or the effect of rotation, it is impossible to release either the muzzle safety or the self-destroying arrangement.

Upon discharge, the projectile is given a rotational spin of about 30,000 rpm or more. As a result, the various pivoted elements are acted upon by the resulting centrifugal force and will pivot outwardly. Thus the metal flaps 39 are moved outwardly, as indicated in FIG. 5. As a result, the anchor 28 of the timer is released and the timer will start to run down under the effect of the draw spring 24 which had been cocked during assembly. Consequently, the spring core 22, including the lower extension 22a and the stop surfaces 22a and 22a will rotate (see FIG. 6).

The safety lever 20, securing the safety nut 13 against rotation as it encompasses the safety nut, also is acted upon by the centrifugal force and will attempt to swing to the dash-dot position shown in FIG. 6, counter to the effect of the spring 21. It will be prevented from doing so by means of the lug 20c which engages behind the stop surface 22a, of the lower extension 22a of the spring core. Only when the lower extension 22a of the spring core has turned by an angle a (FIG. 6), will the lug 200 be released from the stop surface 22a At this point, the safety lever 20 can swivel into the dash-dot position shown in FIG. 6, whereby the leaf spring 21 is deflected. The force of the spring 21 will be overcome by the outwardly urged lever 20 at approximately 30,000 rpm. When the safety lever 20 swivels outwardly, the safety nut 13 will be disengaged from the safety lever 20, so that it is no longer secured against turning. The positional arrangement of the stop surfaces 22a, and 22a;, will be selected during mounting of the fuse, and will be dependent upon how great a muzzle safety of the fuse is desired.

The steel loop 15 enclosing centrifugal strip 14 is released, as a result of the spinning and the resulting centrifugal force of the projectile. Consequently, the centrifugal strip 14 begins to unwind. As a result, the safety nut 13 is turned in such a direction that the safety bushing 40 is screwed upwardly into the safety nut 13. Therefore, the safety bushing 40 is pulled out of the stopping recess 16a of the rotor 16, and the rotor will turn, under the influence of the centrifugal force, into such a position that the primer 17 will come into the path of movement of the firing pin 35. If the projectile should now strike a target, the firing pin will penetrate into the primer, as a result of which the latter is made to explode.

If the projectile does not strike a target within a predetermined time, then it must still be assured that selfdestruction will occur. This is accomplished through the fact that, with further turning of the spring core 22, the moving nut, as already described, is moved toward the spring housing 30. As a result, the arms 32a of the levers 32 are released. Consequently, these levers 32 are swung to the outside by centrifugal force, as shown in FIG. 2. Therefore, the striking bushing 34 is freed which, under the bias of the spring 36, will drive the firing pin 35 into the primer 17.

The largest possible angle a, which has been illustrated in FIG. 6, corresponds to an angle of 72. This means that if the spring core 22 accomplishes one revolution per second, this angle of 72 is traversed in onefifth of a second. The muzzle safety therefore amounts to one-fifth of a second. If one assumes that the starting velocity of a projectile amounts to about 800 meters per second, then in such a case there results a muzzle safety path of 160 meters from the lever 20. The centrifugal strip 14 then unwinds, which, according to a preferred form of the invention, results in a further safety of about to meters. Naturally, by making angle a smaller, any desired muzzle safety under 160 meters can be achieved. In the case of an angle of 20, there will be one-eighteenth of a second, for a muzzle safety path of about 44 meters (800/ 18), plus an additional 15 to 20 meters as a result of the unwinding of the centrifugal strip 14. This 20 angle is the extreme position of the safety lever 20 in which the latter can still safely encompass the parallel surfaces 13b of the safety nut 13.

It should be noted that during the turning of the lower extension 220 of the spring core, and after the lever 20 has been unlocked from the lug 200, the leaf spring 21 has an important task to fulfill in maintaining a bias on the safety lever 20 for preventing the safety lever from swinging out due merely, for example, to the force of gravity which, as a consequence, would cause a premature release of the safety nut 13.

The timing mechanism 22, 24 through 28 and 31 through 33a for the self-destroying element is, as already described, in operative connection with the arrangement for the muzzle safety via the extension 22a of the spring core. The timing mechanism may be considered as being divided into three subgroups, which are in close functional connection with one another, namely:

a drive, independent of centrifugal force, including the draw spring 24;

a timer for regulating the running down of the timing mechanism, comprising a single pair of gears and 27, with a drive wheel 26, and

the particular releasing device for the self-destroying element 34.

The timer, which was described previously, further includes the anchor 28, which is rotatably mounted on the extension 22a of the spring core 22. The draw spring 24 which drives the timer is precocked by a predetermined amount during assembly by winding the spring core 22 (see FIG. 3). For that purpose, the extension 22b of the spring core has a screw nick 22c adapted to receive a suitable winding tool (see FIG. 2). The amount of precocking is preferably such that the spring core 22 can execute eight revolutions.

To set the time for the self-destroying element 34, the spring core 22 is rotated by means of the tool which is inserted into the screw nick 22c. In order to prevent relative movement from occurring between the upper spring core extension 22b and the movable nut 31 during this initial setting, the guide element 33 can be removed, with the fuse housing 10 being disassembled. The guide element 33 has a plurality of tabs 33b attached at its base. The tabs are insertable into diametrically arranged, upwardly opening recesses in the stationary spring housing 23 to prevent rotation of the guide element. The guide element 33 thus can be lifted off of the cover 30 of the spring housing and off of the movable nut 31 during assembly, and can be replaced again when turned by or 360.

According to the design of the timer in this case, a turn by 360 corresponds to one second. Therefore, the self-destroying time of the fuse can be determined for a precise detonation, during assembly. A fine tuning within one-eighth of a second can be accomplished by the movable nut 31 itself. Since the movable nut 31 has 8 sides, upon adjusting it by one-eighth of a revolution, i.e., 360/8, adjustment by 45 increments is possible after lifting the guide element 33 off of the movable nut. Since a revolution corresponds to one second, a 45 turn equals one-eighth of a second.

It can be seen without difficulty that the fuse according to the invention is simply structured, while at the same time guaranteeing an absolutely safe functioning which is not capable with know fuses.

OPERATION Assembly During assembly, the rotor 16 is turned to the safety position shown in FIG. 1 and the safety bushing 40 is inserted into the stopping aperture 16a to prevent rotation of the rotor. The centrifugal strip 14 of the safety nut 13 is wound tight and secured in its tightened position by the steel loop 15. The anchor 28 is secured against rotation by the flaps 39.

With the guide element 33 removed, the spring core 22 is turned to wind the draw spring 24 to a desired tension. The movable nut 31, the guide element 33, and the levers 32 are then assembled in a position to secure the firing pin 35 against movement.

As noted previously, the angle a between the lug 20c and the stop surface 220 of the lower extension 22a determines the amount of rotation of the spring core 22 which is necessary to release the safety lever 20. This, then, determines the muzzle safety of the projectile. Pre-Firing Condition It will be apparent that in its pre-firing safety position, the firing pin cannot detonate the primer 17 because the primer is held out of alignment with the firing pin 35 through engagement of the safety bushing 40 within the stopping aperture 16a.

The safety busing, in turn, is held against rotation by the surfaces 11a of the fuse body 11 (see FIG. 9). Sliding movement of the safety bushing occurs when the safety nut 13 rotates.

Rotation of the safety nut is prevented by engagement of the safety nut periphery by the recess 20a in the safety lever 20.

Outward swinging of the safety lever 20 is prevented by the bias of the spring 21 and the engagement of the lug 200 with the stop surface 22a of the lower extension 22a (see FIG. 6). While the bias of the spring 21 can be overcome by centrifugal force, the securement provided by the lug 200 can only be overcome by rotation of the lower extension by an angle a.

Rotation of the lower extension 22a of the spring core 22 is constrained by the connection of the gear 25, attached to the spring core 22, with the anchor 28. In other words, the anchor 28 is prevented from turning by the metal flaps 39 (see FIG. Since the gear 25 is connected with the anchor 28 through the drive wheel 26 and the gear wheel 27, the latter being turnable only upon release of the anchor, there can be no rotation of the spring core.

As noted previously, even should the connection between the gear 25 and the anchor 28 be broken, as by an accidental impact during firing, the spring core 22 can only rotate to the position at which the portion defined by the stop surface 22a,, and the outer periphery of the lower extension becomes jammed within the notch d. Such an occurrence renders the fuse inoperative since the safety lever 20 cannot swing outwardly to release the safety nut 13.

In the safety position, the firing pin 35 is kept in a raised position by the spring 38 and is separated from the downwardly biased firing bushing by the pivoted levers 32.

Detonation Upon firing, the projectile is subjected to an initial, high amount of rotational spin. Although the centrifugal force becomes sufficient to overcome the inward bias of both the flaps 39 and the spring 21, only the flaps 39 move outwardly, since the lug 200 of the safety lever 20 is still engaging the stop surface 22a Thus, the anchor 28 is released and the draw spring 24 begins to unwind, rotating the spring core 22 accordingly. This rotation is slow, however, since the anchor 28 tends to act as an escapement and to resist the rotation of the gear wheel 27.

After the lower extension 22a of the spring core has turned by an angle a, the safety lever 20 is freed and swings outwardly against the spring 21 by centrifugal force. The safety nut 13 is now free to rotate under the influence of the centrifugal strip 14 and the safety bushing 40 is drawn upwardly to become disengaged from the rotor 16. The rotor then turns, under centrifugal force, to a position where the primer 17 is aligned with the firing pin 35.

Until this point, there has been no possibility of detonation, and the amount of travel of the projectile from the muzzle defines the muzzle safety. It is determined by the initial setting of the stop surface 22a; since the angle 0: determines how much rotation is required of the spring core 22 to cause a release of the safety bush- Once the primer 17 becomes aligned with the firing pin 35, detonation may occur upon an impact caused by the projectile striking a target. Should no such impact be forthcoming, then the timing mechanism winds down and enables the spring 36 to push the firing pin into the primer.

In this latter-regard, it is apparent that as the spring core continues to rotate, under the bias of the draw spring 24, themovable nut 31 will travel downwardly, within its predetermined time span, to the dash-dot position shown in FIG. 1. At this point, the levers 32 are able to swing outwardly under the influence of centrifugal force. When this occurs, the biased firing bushing 34 pushes the firing pin into the primer 17 to detonate the projectile.

ADVANTAGES AND SCOPE OF THE INVENTION The present invention provides a fuse which exhibits required muzzle safety characteristics while affording certain detonation of the projectile.

The positive engagement between the stop surface 22a and the lug 200 provides assurance that the muzzle safety will not become jeopardized by unexpected variations in the amounts of projectile spinning or by accidental impacts.

Moreover, the adjustability of the location of the stop surface 22a. provides a precise variation of the amount of muzzle safety.

The structural arrangement of the firing pin and firing bushing assures that the firing pin, when urged toward the primer, will travel at high speed to insure a proper control over the occurrance of detonation.

The arrangement of the stop surface 22a and the notch 20d provides a positive safety mechanism for preventing firing as a result of inadvertent impacts. This enables the projectiles to be safely transported.

The adjustability feature of the relative position between the arms 32a and the movable nut 31 enables precise variations in the occurrence of self-destruction to be made.

Although the invention has been described in connection with a preferred embodiment thereof, it will be appreciated by those skilled in the art that additions, modifications, substitutions and deletions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A detonating fuse for use in combination with an explosive projectile and comprising:

a firing pin mounted for longitudinal movement;

a primer-mounting rotor for supporting a primer mechanism of an explosive charge;

said rotor being mounted for movement between:

a safety position wherein firing engagement between said primer and said firing pin is prevented, and

a firing position wherein firing engagement between said primer and said firing pin is permitted;

biasing means adapted to bias said firing pin from a rest position to a firing position within said rotor;

a safety nut being rotatably mounted around said firing pin;

drive means, including a centrifugal strip, being attached to said safety nut for imparting rotation thereto;

a safety element being threadably connected to said safety nut and being longitudinally shiftable along said firing pin, in response to rotation of said safety nut, between:

a first position wherein said safety element engages a stop recess of said rotor to hold said rotor in its safety position, and

a second position wherein said safety element and said rotor are out of stopping engagement;

a nut-locking mechanism being movable between:

a locking position in which it operatively engages and prevents rotation of said safety nut, and

a release position to which it is movable by centrifugal force so as to release said safety nut for rotation;

a core member mounted for rotation around said firing pin and including first and second extensions;

said first extension having means for:

securing said nut-locking mechanism in its locking position, and

freeing said nut-locking mechanism, in response to a predetermined rotational movement of said core member, to permit movement thereof to its release position;

a restraining mechanism located adjacent said biasing means and being movable between:

a restraining position wherein said biasing means is prevented from moving said firing pin to its firing position, and

a release position wherein said biasing means is free to move said firing pin to its firing position;

a movable nut being threadably secured to said second extension and being mounted thereon for nonrotatable, longitudinal shifting movement along said firing pin, in response to rotation of said core member, between:

a first position in which said restraining mechanism is held in its restraining position, and

a second position in which said restraining mechanism is free to move to its release position;

a draw spring being operatively connected to said core member to cause rotation thereof; and

timer means connected to said core body to regulate the rate of rotation of said core member;

rotation of said core member by a predetermined amount, for releasing said nut locking means, being required to enable said projectile to be detonated.

2. A fuse according to claim 1 wherein said nutlocking means comprises:

a safety lever being pivotally mounted on one end for movement from its rest position to its release position in response to centrifugal force;

said safety lever having at least one recess portion at its other end, said one recess portion encompassing said safety nut to hold said safety nut against rotation, while said safety lever is in its rest position.

3. A fuse according to claim 2 wherein:

said first extension of said core member is provided with-at least one stop surface;

said safety lever being provided with:

another recess portion at said other end for encompassing said first extension when said safety lever is in its rest position, and

a lug projecting into said other recess;

said one stop surface and said lug being arranged such that pivotal movement of said safety lever into its release position is prevented by engagement of said one stop surface and said lug;

rotation of said core member by a predetermined amount causing said one stop surface to be moved to a position enabling said safety lever to be swung to its release position.

4. A fuse according to claim 2 wherein:

said safety lever is provided with another recess portion for encompassing said first extension;

said other recess portion including a notch;

said first extension being provided with a stop surface;

said notch and said stop surface being arranged such that rotation of said core member within said other recess portion causes an extension part, defined by said stop surface and the outer periphery of said first extension, to become jammed into said notch, in the absence of a force tending to move said safety lever to its release position.

5. A fuse according to claim 1 wherein said timer means comprises:

a gear mounted on said core member;

a drive wheel drivingly connected to said gear;

a gear wheel rotatably connected to said gear, and

an anchor means mounted for engagement with said gear wheel.

6. A fuse according to claim 5 wherein said anchor means is rotatably mounted on said first extension of the spring core.

7. A fuse according to claim 1 wherein said restraining mechanism comprises:

at least one swingable lever pivotally mounted exter nally of said firing pin;

said swingable lever including an arm which, in an inwardly swung position of said swingable lever, projects into a bore provided in said movable nut, to define the restraining position of said restraining mechanism;

said arm and said movable nut being arranged such that, in response to a predetermined longitudinal shifting of said movable nut, said arm is freed from said bore to enable said swingable lever to pivot, in response to centrifugal force, to an outwardly swung position to define the release position of said restraining mechanism.

8. A fuse according to claim 7 wherein:

a guide element is positioned to encompass a noncircular outer periphery of said movable nut;

said guide element being arranged to prevent rotation of said movable nut relative to said upper extension of said core member.

9. A fuse according to claim 8 wherein the pivotal mounting of said swingable lever is on said guide element.

10. A fuse according to claim 8 wherein:

said draw spring is mounted in a spring housing member;

said guide element being provided with tabs which are removably engageable in recesses in said spring housing.

11. A fuse according to claim 1 wherein:

a guide element is positioned to encompass a noncircular outer periphery of said movable nut;

said guide element being arranged to prevent rotation of said movable nut relative tosaid upper extension of said core member.

12. A fuse according to claim 1 and further including:

means for securing said core member against rotation and being movable by centrifugal force to a position wherein said core member may be rotated by said draw spring.

13. A fuse according to claim 2 wherein:

said core member is provided with spring means for biasing said firing pin to its rest position;

said safety lever being provided with spring means for biasing said safety lever to its rest position.

14. A detonating fuse for use in combination with an explosive projectile and comprising:

a firing pin mounted for longitudinal movement;

primer-mounting means for supporting a primer mechanism of an explosive charge;

said primer-mounting means being mounted for movement between:

a safety position wherein firing engagement between said primer and said firing pin is prevented, and

a firing position wherein firing engagement between said primer and said firing pin is permitted;

biasing means adapted to bias said firing pin from a rest position within said primer-mounting means;

a safety nut being rotatably mounted around said firing pin;

drive means attached to said safety nut for imparting rotation thereto;

a safety element being threadably connected to said safety nut and being longitudinally shiftable along said firing pin, in response to rotation of said safety nut, between:

a first position wherein said safety element engages a stop portion of said primer-mounting means to hold said primer-mounting means in its safety position, and

a second position wherein said safety element and said primer-mounting means are out of stopping engagement;

a nut-locking mechanism being movable between:

a locking position in which it operatively engages and prevents rotation of said safety nut, and

a release position to which it is movable by centrifugal force so as to release said safety nut for rotation;

a core member mounted for rotation around said firing pin and including first and second extensions;

said first extension having means for:

securing said nut-locking mechanism in its locking position, and

freeing said nut-locking mechanism, in response to a predetermined rotational movement of said core member, to permit movement thereof to its release position;

a restraining mechanism located adjacent said biasing means and being movable between:

a restraining position wherein said biasing means is prevented from moving said firing pin to its firing position, and

a release position wherein said biasing means is free to move said firing pin to its firing position;

a movable nut being threadably secured to said second extension and being mounted thereon for nonrotatable, longitudinal shifting movement along said firing pin, in response to rotation of said core member, between:

a first position in which said restraining mechanism is held in its restraining position, and

a second position in which said restraining mechanism is free to move to its release position;

a draw spring being operatively connected to said core member to cause rotation thereof; and

timer means connected to said core body to regulate the rate of rotation of said core member;

rotation of said core member by a predetermined amount, for releasing said nut locking means, being required to enable said projectile to be detonated.

15. A detonating fuse for use in combination with an explosive projectile and comprising:

a firing pin mounted for longitudinal movement;

primer-mounting means for supporting a primer mechanism of an explosive charge;

said primer-mounting means being mounted for movement between:

a safety position wherein firing engagement between said primer and said firing pin is prevented, and

a firing position wherein firing engagement between said primer and said firing pin is permitted;

biasing means adapted to bias said firing pin from a rest position within said primer-mounting means;

a safety nut being rotatably mounted around said firing pin;

drive means attached to said safety nut for imparting rotation thereto;

a safety element being threadably connected to said safety nut and being longitudinally shiftable along said firing pin, in response to rotation of said safety nut, between:

a first position wherein said safety element engages a stop portion of said primer-mounting means to hold said primer-mounting means in its safety position, and

a second position wherein said safety element and said primer-mounting means are out of stopping engagement;

a nut-locking mechanism being movable between:

a locking position in which it operatively engages and prevents rotation of said safety nut, and

a release position to which it is movable by centrifugal force so as to release said safety nut for rotation;

a core member mounted for rotation around said firing pin and including first and second extensions;

said first extension having means for:

securing said nut-locking mechanism in its locking position, and

freeing said nut-locking mechanism, in response to a predetermined rotational movement of said core member, to permit movement thereof to its release position;

a restraining mechanism located adjacent said biasing means and being movable between:

a restraining position wherein said biasing means is prevented from moving said firing pin to its firing position, and

a release position wherein said biasing means is free to move said firing pin to its firing position;

a movable nut being threadably secured to said second extension and being mounted thereon for nonrotatable, longitudinal shifting movement along said firing pin, in response to rotation of said core member, between:

a first position in which said restraining mechanism is held in its restraining position, and

a second position in which said restraining mechanism is free to move to its release position;

a draw spring being operatively connected to said core member to cause rotation thereof; and

timer means connected to said core body to regulate the rate of rotation of said core member; said nut-locking means including:

a safety lever being pivotally mounted at one end for movement from said rest position to said release position in response to centrifugal force;

said safety lever having first and second recess portions at its other end;

said first recess portion encompassing said safety nut while in the rest position of said safety lever to hold said safety nut against rotation;

said first extension of said core member being provided with first and second stop surfaces;

said second recess portion of said safety lever encompassing said first extension when said safety leve is in its rest position;

a lug being provided on said safety lever and projecting into said second recess portion;

said first stop surface and said lug being arranged such that pivotal movement of said safety lever into its release position is prevented by engagement of said first stop surface and said lug;

rotation of said core member by a predetermined amount causing said first stop surface to be moved to a position enabling said safety lever to be swung to its release position;

said second recess portion further including a notch;

said notch and said second stop surface being arranged such that rotation of said core member within said second recess portion causes said second stop surface to engage said notch, in the absence of a force tending to move said safety lever to its release position; said timing means including:

a gear mounted for rotation on said core member; a rotatably mounted gear wheel,

a drive means drivingly interconnecting said gear wheel to said gear, and

rotatable anchor means mounted for engagement with said gear wheel to regulate the rotation of said gear wheel;

said anchor means including means for securing said anchor means and said core member against rotation and being movable, in response to centrifugal force, to a position releasing said anchor means and said core member for rotation by said draw spring; said restraining mechanism including:

at least one swingable lever pivotally mounted externally of said firing pin;

said swingable lever including an arm which, in an inwardly swung position of said swingable lever, projects into a bore provided in said movable nut, to define the restraining position of said restraining mechanism,

said arm and said movable nut being arranged such that, in response to a predetermined longitudinal shifting of said movable nut, said arm is freed from said bore to enable said swingable lever to pivot under the influence of centrifugal force to an outwardly swung position to define the release position of said restraining mechanism;

a guide element being arranged to encompass a noncircular outer periphery of said movable nut to prevent rotation of said movable nut relative to said second extension of said core member;

rotation of said core member by a predetermined amount, for releasing said nut-locking means, being required to enable said projectile to be detonated. 

1. A detonating fuse for use in combination with an explosive projectile and comprising: a firing pin mounted for longitudinal movement; a primer-mounting rotor for supporting a primer mechanism of an explosive charge; said rotor being mounted for movement between: a safety position wherein firing engagement between said primer and said firing pin is prevented, and a firing position wherein firing engagement between said primer and said firing pin is permitted; biasing means adapted to bias said firing pin from a rest position to a firing position within said rotor; a safety nut being rotatably mounted around said firing pin; drive means, including a centrifugal strip, being attached to said safety nut for imparting rotation thereto; a safety element being threadably connected to said safety nut and being longitudinally shiftable along said firing pin, in response to rotation of said safety nut, between: a first position wherein said safety element engages a stop recess of said rotor to hold said rotor iN its safety position, and a second position wherein said safety element and said rotor are out of stopping engagement; a nut-locking mechanism being movable between: a locking position in which it operatively engages and prevents rotation of said safety nut, and a release position to which it is movable by centrifugal force so as to release said safety nut for rotation; a core member mounted for rotation around said firing pin and including first and second extensions; said first extension having means for: securing said nut-locking mechanism in its locking position, and freeing said nut-locking mechanism, in response to a predetermined rotational movement of said core member, to permit movement thereof to its release position; a restraining mechanism located adjacent said biasing means and being movable between: a restraining position wherein said biasing means is prevented from moving said firing pin to its firing position, and a release position wherein said biasing means is free to move said firing pin to its firing position; a movable nut being threadably secured to said second extension and being mounted thereon for non-rotatable, longitudinal shifting movement along said firing pin, in response to rotation of said core member, between: a first position in which said restraining mechanism is held in its restraining position, and a second position in which said restraining mechanism is free to move to its release position; a draw spring being operatively connected to said core member to cause rotation thereof; and timer means connected to said core body to regulate the rate of rotation of said core member; rotation of said core member by a predetermined amount, for releasing said nut locking means, being required to enable said projectile to be detonated.
 2. A fuse according to claim 1 wherein said nut-locking means comprises: a safety lever being pivotally mounted on one end for movement from its rest position to its release position in response to centrifugal force; said safety lever having at least one recess portion at its other end, said one recess portion encompassing said safety nut to hold said safety nut against rotation, while said safety lever is in its rest position.
 3. A fuse according to claim 2 wherein: said first extension of said core member is provided with at least one stop surface; said safety lever being provided with: another recess portion at said other end for encompassing said first extension when said safety lever is in its rest position, and a lug projecting into said other recess; said one stop surface and said lug being arranged such that pivotal movement of said safety lever into its release position is prevented by engagement of said one stop surface and said lug; rotation of said core member by a predetermined amount causing said one stop surface to be moved to a position enabling said safety lever to be swung to its release position.
 4. A fuse according to claim 2 wherein: said safety lever is provided with another recess portion for encompassing said first extension; said other recess portion including a notch; said first extension being provided with a stop surface; said notch and said stop surface being arranged such that rotation of said core member within said other recess portion causes an extension part, defined by said stop surface and the outer periphery of said first extension, to become jammed into said notch, in the absence of a force tending to move said safety lever to its release position.
 5. A fuse according to claim 1 wherein said timer means comprises: a gear mounted on said core member; a drive wheel drivingly connected to said gear; a gear wheel rotatably connected to said gear, and an anchor means mounted for engagement with said gear wheel.
 6. A fuse according to claim 5 wherein said anchor means is rotatably mounted On said first extension of the spring core.
 7. A fuse according to claim 1 wherein said restraining mechanism comprises: at least one swingable lever pivotally mounted externally of said firing pin; said swingable lever including an arm which, in an inwardly swung position of said swingable lever, projects into a bore provided in said movable nut, to define the restraining position of said restraining mechanism; said arm and said movable nut being arranged such that, in response to a predetermined longitudinal shifting of said movable nut, said arm is freed from said bore to enable said swingable lever to pivot, in response to centrifugal force, to an outwardly swung position to define the release position of said restraining mechanism.
 8. A fuse according to claim 7 wherein: a guide element is positioned to encompass a non-circular outer periphery of said movable nut; said guide element being arranged to prevent rotation of said movable nut relative to said upper extension of said core member.
 9. A fuse according to claim 8 wherein the pivotal mounting of said swingable lever is on said guide element.
 10. A fuse according to claim 8 wherein: said draw spring is mounted in a spring housing member; said guide element being provided with tabs which are removably engageable in recesses in said spring housing.
 11. A fuse according to claim 1 wherein: a guide element is positioned to encompass a non-circular outer periphery of said movable nut; said guide element being arranged to prevent rotation of said movable nut relative to said upper extension of said core member.
 12. A fuse according to claim 1 and further including: means for securing said core member against rotation and being movable by centrifugal force to a position wherein said core member may be rotated by said draw spring.
 13. A fuse according to claim 2 wherein: said core member is provided with spring means for biasing said firing pin to its rest position; said safety lever being provided with spring means for biasing said safety lever to its rest position.
 14. A detonating fuse for use in combination with an explosive projectile and comprising: a firing pin mounted for longitudinal movement; primer-mounting means for supporting a primer mechanism of an explosive charge; said primer-mounting means being mounted for movement between: a safety position wherein firing engagement between said primer and said firing pin is prevented, and a firing position wherein firing engagement between said primer and said firing pin is permitted; biasing means adapted to bias said firing pin from a rest position within said primer-mounting means; a safety nut being rotatably mounted around said firing pin; drive means attached to said safety nut for imparting rotation thereto; a safety element being threadably connected to said safety nut and being longitudinally shiftable along said firing pin, in response to rotation of said safety nut, between: a first position wherein said safety element engages a stop portion of said primer-mounting means to hold said primer-mounting means in its safety position, and a second position wherein said safety element and said primer-mounting means are out of stopping engagement; a nut-locking mechanism being movable between: a locking position in which it operatively engages and prevents rotation of said safety nut, and a release position to which it is movable by centrifugal force so as to release said safety nut for rotation; a core member mounted for rotation around said firing pin and including first and second extensions; said first extension having means for: securing said nut-locking mechanism in its locking position, and freeing said nut-locking mechanism, in response to a predetermined rotational movement of said core member, to permit movement thereof to its release position; a restraining mechanism locaTed adjacent said biasing means and being movable between: a restraining position wherein said biasing means is prevented from moving said firing pin to its firing position, and a release position wherein said biasing means is free to move said firing pin to its firing position; a movable nut being threadably secured to said second extension and being mounted thereon for non-rotatable, longitudinal shifting movement along said firing pin, in response to rotation of said core member, between: a first position in which said restraining mechanism is held in its restraining position, and a second position in which said restraining mechanism is free to move to its release position; a draw spring being operatively connected to said core member to cause rotation thereof; and timer means connected to said core body to regulate the rate of rotation of said core member; rotation of said core member by a predetermined amount, for releasing said nut locking means, being required to enable said projectile to be detonated.
 15. A detonating fuse for use in combination with an explosive projectile and comprising: a firing pin mounted for longitudinal movement; primer-mounting means for supporting a primer mechanism of an explosive charge; said primer-mounting means being mounted for movement between: a safety position wherein firing engagement between said primer and said firing pin is prevented, and a firing position wherein firing engagement between said primer and said firing pin is permitted; biasing means adapted to bias said firing pin from a rest position within said primer-mounting means; a safety nut being rotatably mounted around said firing pin; drive means attached to said safety nut for imparting rotation thereto; a safety element being threadably connected to said safety nut and being longitudinally shiftable along said firing pin, in response to rotation of said safety nut, between: a first position wherein said safety element engages a stop portion of said primer-mounting means to hold said primer-mounting means in its safety position, and a second position wherein said safety element and said primer-mounting means are out of stopping engagement; a nut-locking mechanism being movable between: a locking position in which it operatively engages and prevents rotation of said safety nut, and a release position to which it is movable by centrifugal force so as to release said safety nut for rotation; a core member mounted for rotation around said firing pin and including first and second extensions; said first extension having means for: securing said nut-locking mechanism in its locking position, and freeing said nut-locking mechanism, in response to a predetermined rotational movement of said core member, to permit movement thereof to its release position; a restraining mechanism located adjacent said biasing means and being movable between: a restraining position wherein said biasing means is prevented from moving said firing pin to its firing position, and a release position wherein said biasing means is free to move said firing pin to its firing position; a movable nut being threadably secured to said second extension and being mounted thereon for non-rotatable, longitudinal shifting movement along said firing pin, in response to rotation of said core member, between: a first position in which said restraining mechanism is held in its restraining position, and a second position in which said restraining mechanism is free to move to its release position; a draw spring being operatively connected to said core member to cause rotation thereof; and timer means connected to said core body to regulate the rate of rotation of said core member; said nut-locking means including: a safety lever being pivotally mounted at one end for movement from said rest position to said release position in respOnse to centrifugal force; said safety lever having first and second recess portions at its other end; said first recess portion encompassing said safety nut while in the rest position of said safety lever to hold said safety nut against rotation; said first extension of said core member being provided with first and second stop surfaces; said second recess portion of said safety lever encompassing said first extension when said safety lever is in its rest position; a lug being provided on said safety lever and projecting into said second recess portion; said first stop surface and said lug being arranged such that pivotal movement of said safety lever into its release position is prevented by engagement of said first stop surface and said lug; rotation of said core member by a predetermined amount causing said first stop surface to be moved to a position enabling said safety lever to be swung to its release position; said second recess portion further including a notch; said notch and said second stop surface being arranged such that rotation of said core member within said second recess portion causes said second stop surface to engage said notch, in the absence of a force tending to move said safety lever to its release position; said timing means including: a gear mounted for rotation on said core member; a rotatably mounted gear wheel, a drive means drivingly interconnecting said gear wheel to said gear, and rotatable anchor means mounted for engagement with said gear wheel to regulate the rotation of said gear wheel; said anchor means including means for securing said anchor means and said core member against rotation and being movable, in response to centrifugal force, to a position releasing said anchor means and said core member for rotation by said draw spring; said restraining mechanism including: at least one swingable lever pivotally mounted externally of said firing pin; said swingable lever including an arm which, in an inwardly swung position of said swingable lever, projects into a bore provided in said movable nut, to define the restraining position of said restraining mechanism, said arm and said movable nut being arranged such that, in response to a predetermined longitudinal shifting of said movable nut, said arm is freed from said bore to enable said swingable lever to pivot under the influence of centrifugal force to an outwardly swung position to define the release position of said restraining mechanism; a guide element being arranged to encompass a non-circular outer periphery of said movable nut to prevent rotation of said movable nut relative to said second extension of said core member; rotation of said core member by a predetermined amount, for releasing said nut-locking means, being required to enable said projectile to be detonated. 